The self assembly of supramolecular structures that are ordered on the nanometer scale is a key objective in nanotechnology. DNA and peptide nanotechnologies have produced various two- or three-dimensional structures, but protein molecules have been under exploited in this area of research.
It has been shown that genetic fusion of subunits from protein assemblies that have matching rotational symmetry generates species that can self-assemble in to well-ordered, pre-determined one-, two- and three-dimensional arrays that are stabilised by extensive intermolecular interactions. The supramolecular structures produced in this way are distinguished from protein crystals produced using conventional methods and are described in Sinclair et al. (2011) Nature Nanotechnology 6:558:562.
Supramolecular structures may be generated by the genetic fusion of peptide chains that derive from multi-subunit protein assemblies that have rotational symmetry axes of equal order. Binary structures are formed from discrete entities, termed “components”. A binary structure comprises a first component formed by fusing a peptide chain from a homologous protein assembly (multi-subunit protein) to a peptide chain from a heterologous protein assembly (comprising two or more types of subunit). The second component of the binary structure comprises the second subunit from the heterologous protein assembly. When these complementary components are mixed, they self-assemble to form a supramolecular structure.
The components derived from multi-subunit protein assemblies naturally assemble to form regular lattices as a result of their neighbouring components being connected by two or more symmetrically equivalent interactions. As a consequence of this, the components are compelled to align along their common symmetry axis, imposing a fixed relative disposition of neighbouring subunits. Details of the required symmetries are disclosed in Sinclair et al., WO 2004/033487, and WO 2008/145951.
Sinclair et al. describe one-dimensional and two-dimensional protein lattices and disclose that the solid-phase materials produced using their preliminary designs for self-assembling binary three-dimensional lattices lack sufficient long-range order to permit study by X-ray diffraction. Therefore, there remains a need to develop methods to improve lattice order and facilitate the growth of larger crystals.